Lecture 16: Zone Air Paths and Air Distribution Units Notes: __________________________________________________________________ ________________________________________________________________________ Material prepared by GARD Analytics, Inc. and University of Illinois at Urbana-Champaign under contract to the National Renewable Energy Laboratory. All material Copyright 2002-2003 U.S.D.O.E. - All rights reserved

Purpose of this Lecture Gain an understanding of how to: Define the Zone Equipment (Demand Side) of an Air Loop Zone Air Supply and Return Paths Air Distribution Units Examples of Zone Equipment

Keywords Covered in this Lecture Fan:Simple:VariableVolume Zone Air Supply Path Zone Air Return Path Zone Splitter and Zone Mixer (review) Direct Air Air Distribution Unit Single Duct:VAV:Reheat

Air Loop Components: Simple Example FAN:SIMPLE:VariableVolume, Supply Fan 1, !- Fan Name FanAvailSched, !- Available Schedule 0.7, !- Fan Total Efficiency 600.0, !- Delta Pressure {Pa} 1.56, !- Max Flow Rate {m3/s} 0.45, !- Min Flow Rate {m3/s} 0.9, !- Motor Efficiency 1.0, !- Motor In Airstream Fraction 0.35071223, !- FanCoefficient 1 0.30850535, !- FanCoefficient 2 -0.54137364, !- FanCoefficient 3 0.87198823, !- FanCoefficient 4 0.000, !- FanCoefficient 5 Main Heating Coil 1 Outlet Node, !- Fan_Inlet_Node VAV Sys 1 Outlet Node; !- Fan_Outlet_Node

Zone Equipment Syntax Map

Air Path Zone Supply Air Path Zone Return Air Path

Zone Supply Air Path Zone splitter Zone supply plenum Splits the supply air from the main air handler to serve individual zones Dual duct systems require splitters for both the cold and hot air ducts Zone supply plenum Allows system air to flow through a zone before it reaches the zone(s) to be served One supply plenum per air handler supply duct

Zone Supply Air Path -Example ZONE 3 ATU In Node ZONE3 ZONE2 ATU ZONE2 ZONE1 ATU ZONE1 Zone Eq Zone Supply Air Splitter 1 Zone Supply Air Path 1 Supply Fan Exhaust

Zone Supply Air Path - Example (cont’d) Zone Supply Air Path 1, !- name of object Zone Eq In Node, !- supply path inlet node Zone Splitter, Zone Supply Air Splitter 1; !- type and name of component ZONE SPLITTER, Zone Supply Air Splitter 1, !- name Zone Eq In Node, !- inlet node ZONE1 ATU In Node, !- outlet nodes ZONE2 ATU In Node, ZONE3 ATU In Node;

Zone Return Air Path Zone Mixer Zone return plenum Mixes the return air streams returning to the main air handler from individual zones Zone return plenum Allows system air to flow through a zone before it reaches the main return duct Allows system air to be mixed from multiple zones, can eliminate the need for a zone mixer Can mix plenum and ducted returns Plenums may be in series or parallel (series temperatures lag by a zone time step)

Zone Return Air Path - Example Outlet Node ZONE3 ZONE2 ZONE1 Return Air Mixer Outlet Zone Return Air Mixer Zone Return Air Path Supply Fan Exhaust

Zone Return Air Path – Example with Return Plenum

Zone Return Air Path - Example (cont’d) TermReheatReturnPath, !- Return Air Path Name Return Air Mixer Outlet, !- Return Air Path Outlet Node Zone Mixer, !- KEY--System Component Type 1 Zone Return Air Mixer; !- Component Name 1 ZONE MIXER, Zone Return Air Mixer, !- Mixer Name Return Air Mixer Outlet, !- Outlet_Node Zone 1 Outlet Node, !- Inlet_Node_1 Zone 2 Outlet Node, !- Inlet_Node_2 Zone 3 Outlet Node; !- Inlet_Node_3

Air Loop Zone Equipment Direct Air Air Distribution Units

Zone Equipment Schematic Local Con - vective Units Air HP Unit Heater/ Vent ilator Fan Coil Window AC High Temp Radiant/ Low Radiant Base b oards Radiators Panels Select One Select One Return Air Path Zone Exhaust Branch (Opt.) None Dual Duct Constant Volume (CV) Single Duct CV Reheat VAV VAV: Loca l Conv. Unit Alternatives Hi Temp Rad/Conv Alternatives Low Temp Rad Distribution Options Zone Supply Air Splitter Water HP & Ground Source

Direct Air Used to model systems in which central system air is supplied directly to a zone Furnace Heat pump Central supply air may be controlled to meet setpoints in a “control zone” “Slave zones” typically have no individual control “Slave zones” may have baseboards or other equipment to allow individual control

Direct Air - Example DIRECT AIR, Zone1DirectAir, !- Direct Air Name Inlet Node ZONE2 Inlet Node Supply Fan ZONE1 Node ZONE2 Node ZONE1 ZONE2 ZONE1 Out Node ZONE2 Out Node Control Zone with thermostat Slave Zone DIRECT AIR, Zone1DirectAir, !- Direct Air Name FanAndCoilAvailSched, !- Schedule name for on/off schedule Zone 1 Inlet Node, !- Zone Supply Air Node Name 0.47; !- Maximum air flow rate {m3/s}

Air Distribution Units Allows equipment within the zone inlet duct-work to be attached to the supply air stream Includes equipment that controls or tempers the air going into a zone such as dampers, reheat coils, etc. Only one ADU allowed per zone on a given air loop

Air Distribution Units (cont’d) Single Duct Constant Volume Reheat Single Duct VAV Reheat Dual Duct Constant Volume Dual Duct VAV Powered Induction Units (Series and Parallel)

Air Distribution Units (cont’d) Zone 1 None Dual Duct Constant Volume (CV) Single Duct CV Reheat VAV VAV: Select One Air Distribution Unit Options

Air Distribution Unit - Example SPACE1-1 ATU, ! Name of air distribution unit SPACE1-1 In Node, ! unit outlet node SINGLE DUCT:VAV:REHEAT, ! type of component SPACE1-1 VAV Reheat; ! name of component

Single Duct:VAV:Reheat - Example SPACE1-1 VAV Reheat, ! object name ReheatCoilAvailSched, ! availability schedule SPACE1-1 Zone Coil Air In Node, ! zone heating coil inlet node SPACE1-1 ATU In Node, ! terminal unit inlet node 0.33, ! max air flow rate m3/s 0.3, ! min air flow as decimal fraction of max air flow SPACE1-1 Zone Coil Water In Node, ! water flow control node COIL:Water:SimpleHeating, ! heating component type SPACE1-1 Zone Coil, ! heating component name 0.0003, ! max water flow rate m3/s 0.0, ! min water flow rate m3/s SPACE1-1 In Node, ! terminal unit outlet node 0.001, ! convergence tolerance REVERSE ACTION; ! Damper Heating Action

Summary Zone Equipment loop is the “demand side” of a forced air system Main parts of the zone equipment loop include: Supply and Return paths Thermostats Air Distribution Unit Can also add local radiative or convective systems that serve the zone apart from the air loop